It is well known to produce three-dimensional objects, such as prototype parts, by use of the process known as stereolithography. In stereolithography an elevator is suspended in a vat of liquid resin. A laser beam is manipulated by computer control to cure the resin. The laser beam is traversed across bath and the elevator is successively lowered into the bath to provide step-wise laminar build up of the shape of the desired prototype part. When the desired three-dimensional shape has been formed, the prototype part is raised out of the bath by the elevator.
This stereolithography process is well known and is widely used for making plastic models of component parts for the automotive, aircraft and electronics industries.
One shortcoming of the stereolithographically produced resin models is that the resins employed have considerably less strength than the strength of the materials such as steel, aluminum or plastic which will be used to manufacture the final component. Accordingly, heretofore, the parts manufactured by the stereolithography have generally been limited to use a visualization model to verify the production intent, rather than permitting use as a structural model which can be assembled into a finished product and evaluated for functionality.
The prior art has also recognized that a stereolithographically produced resin plastic model can be used to produce a sample part by investment casting. In this process, the resin model becomes the pattern for the investment processing. Wax gates and vents are attached onto the resin model to form the investment pattern. The pattern is then dipped in a ceramic slurry and cured. An autoclave or other high temperature apparatus is then used to melt away the wax and burn away the resin model. The ceramic mold then can be filled with molten metal such as aluminum to make a high strength functional component part.
In practicing the aforedescribed investment casting process using the resin model, the industry has discovered that the rapid expansion of the resin model during the burning away process has led to stress cracking of the ceramic mold. Accordingly, the industry has developed a process by which the resin model has only a thin outer wall while the internal volume thereof is defined by interconnected support members of very thin cross-section. In this way, the supporting members will collapse readily when subjected to high temperature and will not impose excessive stress on the ceramic mold.
Thus, in view of the above, it will be understood that the industry has developed techniques for effectively using a stereolithographically reproduced resin model to make a pattern for investment casting of an aluminum or other metal prototype part. The metal prototype part can be tested to confirm the functionality of the part, as well as visualize the design of the product.
It would be desirable to further improve the prototyping process by eliminating the need to investment cast prototype parts from the resin model in order to produce a high strength structural part.